CPAP treatment is a common ameliorative treatment for breathing disorders including OSA. CPAP treatment, as described in U.S. Pat. No. 4,944,310, provides pressurized air or other breathable gas to the entrance of a patient's airways at a pressure elevated above atmospheric pressure, typically in the range 4-20 cm H2O.
It is also known for the level of treatment pressure to vary during a period of treatment in accordance with patient need, that form of CPAP being known as automatically adjusting nasal CPAP treatment, as described in U.S. Pat. No. 5,245,995.
NIPPV is another form of treatment for breathing disorders which can involve a relatively higher pressure of gas being provided in the patient mask during the inspiratory phase of respiration and a relatively lower pressure or atmospheric pressure being provided in the patient mask during the expiratory phase of respiration.
In other NIPPV modes the pressure can be made to vary in a complex manner throughout the respiratory cycle. For example, the pressure at the mask during inspiration or expiration can be varied through the period of treatment.
Typically, the ventilatory assistance for CPAP or NIPPV treatment is delivered to the patient by way of a nasal mask. Alternatively, a mouth mask or full face mask or nasal prongs can be used. In this specification any reference to a mask is to be understood as incorporating a reference to a nasal mask, mouth mask, full face mask or nasal prongs.
In this specification any reference to CPAP treatment is to be understood as embracing all of the above described forms of ventilatory treatment or assistance.
A CPAP apparatus broadly comprises a flow generator constituted by a continuous source of air or other breathable gas such as a hospital piped supply or a blower. In the latter case, an electric motor drives the blower and is typically controlled by a servo-controller under the control of a microcontroller unit. In either case, the gas supply is connected to a conduit or tube which in turn is connected to a patient nasal or full-face mask which incorporates, or has in close proximity, an exhaust to atmosphere for venting exhaled gases. Examples of prior art nasal masks are shown in U.S. Pat. Nos. 4,782,832 and 5,243,971.
The supply conduit delivers gas into a chamber formed by walls of the mask. The mask is normally secured to the wearer's head by straps. The straps are adjusted to pull the mask against the face with sufficient force to achieve a gas tight seal between the mask and the wearer's face.
A problem that arises with the use of the existing masks is that in order for the straps to be tight, the mask is compressed against the wearer's face and may push unduly hard on the wearer's nose or face. Additionally, the mask may move around the wearer's face. Thus, there has been hitherto provided a stabilizing support, such as a forehead support, which provides a support mechanism between the mask and the forehead. This forehead support prevents both the mask from pushing too strongly against the wearer's nose and/or facial region (by distributing forces) as well as minimizing movement of the mask with the addition of a contact point between the mask and the wearer's head thereby reducing uncomfortable pressure points. Additionally, the forehead support can be arranged to prevent the gas supply conduit from contacting the wearer's forehead or face.
In order to fit a mask system to a patient, the cushion is fitted to the face of the patient and an ideal position is found. The ideal position is one in which a good seal is formed and the mask feels comfortable to the patient. Once the ideal position is found, the forehead support is brought into contact with the patient's head to provide stability to the ideal position of the mask relative to the patient's head.
Another problem that arises with the use of existing masks is that many forehead supports require two hands to adjust. One hand is typically used to secure the mask, while the other hand is used to adjust the position of the forehead support. Such an adjustment may require too high a level of dexterity for some patients or clinicians. In addition, existing mask systems provide discrete adjustment points for the position of the forehead support, leading to a trial and error process in determining the ideal position. It is also difficult to determine how many discrete positions should be provided. If too few discrete positions are provided, it may not be able to set or lock the forehead support in a position that truly stabilizes the mask in the ideal position. If too many discrete positions are provided, the fitting may be complicated by the patient being unable to decide which position stabilizes the mask in the ideal position.
An even further problem with the use of existing masks is that the adjustment of the forehead support changes the inclination between the forehead support pads and the patient's forehead. For example, the forehead support shown in U.S. Pat. No. 6,532,961 includes a frame that is movably (e.g. pivotably) adjustable with respect to the mask. Pivoting of the forehead support during the adjustment process changes the inclination between the pad and the patient's forehead and may result in an undesirable change in the amount of support provided by the forehead support.
Thus, a need has developed in the art to address one or more of the above problems.